Cutaneous punctures by used needles are common occupational injuries for health care personnel. Of particular concern is the risk these workers incur of contracting a systemic disease such as serum hepatitis or acquired immunodeficiency syndrome.
Most needle-stick injuries occur during disposal of used needles, during the administration of parenteral injections or infusion therapy, drawing blood, recapping needles after use, and handling linens or trash containing uncapped needles. The injury risk associated with simply recapping a hypodermic needle after use is sufficiently great for some institutions to discourage their personnel from recapping used needles. See McCormick, R. D., Maki, D. G., Epidemiology of Needle-Stick Injuries in Hospital Personnel, The American Journal of Medicine, April, 1981, pgs. 928-932. Of course, the uncapped needles pose serious risks during subsequent handling and disposal, particularly if they are not properly disposed of.
Prior inventors have devised hypodermic syringes with movable covers for the needles. Representative examples of this type syringe are disclosed in U.S. Pat. No. 2,876,770 granted Mar. 10, 1959 to R. A. White for "SHIELDED HYPODERMIC SYRINGE" and U.S. Pat. No. 4,664,654 granted May 12, 1987 to E. C. Strauss for "AUTOMATIC PROTRACTING AND LOCKING HYPODERMIC NEEDLE GUARD". The structures proposed in these patents are fairly complex and, hence, costly and therefore do not lend themselves well to mass produced, disposable syringes which are commonly used today. Moreover, both White and Strauss rely on contact between the needle cover and the epidermis of the patient to force the cover back from the point of the needle as the needle penetrates the epidermis. Such contact between the cover and the epidermis is undesirable and, for certain hypodermic applications, impractical.
A much simpler retractable needle cover is disclosed in U.S. Pat. No. 4,139,009 granted Feb. 13, 1979 to M. Alvarez for "HYPODERMIC NEEDLE ASSEMBLY WITH RETRACTABLE NEEDLE COVER". Again, however, retraction of the cover is effected via contact with the epidermis of the patient.
U.S. Pat. No. 3,306,290 granted Feb. 28, 1967 to H. S. Weltman for "AUTOMATICALLY RETRACTABLE NEEDLE SYRINGE" discloses a syringe having a needle cover. In this syringe the needle moves out from the cover when the syringe plunger is actuated to move a fluid carrying carpule forward within the syringe. The needle remains exposed until the syringe is disassembled.
A somewhat related class of medical instruments includes venipuncture catheters which are used to withdraw blood from or infuse liquids into blood vessels. These are indwelling devices, often made of flexible material, which require a sharp pointed instrument, such as a needle, for initial placement, but which require the needle to be either withdrawn or sheathed after placement to prevent damage to the vascular lumen and associated tissue. Examples of this type of device are disclosed in U.S. Pat. No. 3,506,007 granted Apr. 14, 1970 to M. L Henkin for "CATHETER-NEEDLE"; U.S. Pat. No. 3,727,613 granted Apr. 17, 1973 to J. L. Sorenson et al. for "SAFETY CATHETER PLACEMENT ASSEMBLY"; U.S. Pat. No. 4,713,057 granted Dec. 15, 1987 to J. Huttner et al. for "MECHANICAL ASSIST DEVICE FOR INSERTING CATHETERS"; and U.S. Pat. No. 4,627,841 granted Dec. 9, 1986 to R. T. Dorr for "INFUSION NEEDLE". In each of the devices disclosed in the Henkin, Sorenson et al. and Huttner et al. patents when the needles are removed from the catheters they pose the same serious injury risks as do other unsheathed or uncapped syringe needles.
The Dorr infusion needle is a special purpose device in which a blunt end catheter protrudes from a sharp-tipped hollow needle except when the needle is advanced over the catheter for insertion of the device into a blood vessel. Spring means bias the catheter to its indwelling position in which it protrudes from the needle to prevent damage to the vein or other tissue.
There continues to be a need for a self-sheathing hypodermic needle which can be used with syringes and intravenous instruments. See Jagger, J., Hunt, E. H., Brand-Elnagger, J., Pearson, R. D., Rates of Needle-Stick Injury Caused by Various Devices in a University Hospital, The New England Journal of Medicine, Aug. 4, 1988, pgs 284-288.